This invention relates to improvements in a wire coil blast cleaning apparatus, and more particularly to improved radial lifters for use in such an apparatus.
Lengths of wire comprising a plurality of circular coils may be cleaned in an apparatus such as that shown and described in U.S. Pat. No. 4,757,646 to Goetz. Such cleaning is a necessary step in processes for manufacturing a wide variety of objects such as bolts, axles, nails, etc., and is typically performed prior to drawing the wire through a die. The wire must be completely cleaned before it is drawn through the die.
Goetz teaches a wire coil blast cleaning apparatus having a wire coil support in the form of an elongate boom enclosed in a blast cleaning chamber. A length of coiled wire is slipped over the boom, and the boom is then rotated. Rotation of the boom causes rotation of the wire and displacement of the wire longitudinally along the boom.
During rotation of the boom, abrasive cleaning material is directed at the wire at high velocity from a plurality of different angles by a plurality of throwing wheels located within the blast cleaning chamber.
In order to completely clean the wire, abrasive cleaning material must contact surfaces of the wire located between individual coils of wire. The boom taught by Goetz is therefore provided with annular plates, referred to as "splitters", which assist in creating longitudinal spaces between adjacent coils of wire, and radial "lifters" which radially separate coils of wire along the boom. The longitudinal and radial separation of individual wire coils accomplished by the splitters and the lifters allows individual wire coils to be exposed to the abrasive material.
Radial lifters must be resistant to abrasive materials and must be able to support heavy wire coils weighing up to about 6,000 pounds. Therefore, radial lifters such as those taught in the Goetz patent are made from very hard metal alloys, with manganese steel being preferred. Typically, such metal alloys are harder than the wire being cleaned. This results in a number of disadvantages.
Firstly, and most seriously, it has been observed that abrasive cleaning material thrown at the wire becomes trapped between the hard metal lifters and the wire supported on the lifters. This abrasive material is typically in the form of small, round particles referred to as "shot". A typical diameter of such shot is about 0.017 inches. The shot has a hardness greater than that of the wire. Because the lifter is also harder than the wire, particles of abrasive material trapped between the lifter and the wire tend to be driven into and embedded in the wire. After the cleaning process is completed, some of this shot remains embedded in the wire and causes serious problems during subsequent processing steps, such as when the wire is drawn through a die.
Secondly, even if the shot does not remain embedded in the wire after the cleaning step, scratching of the wire caused by the hard metal lifters and the particles of shot driven into the wire is undesirable.
Thirdly, hard metal lifters such as those taught by Goetz have sharp, angular edges. This is due to the fact that hard metal lifters are fabricated by cutting and welding together pieces of sheet metal, rather than being cast from molten metal. It is difficult to fabricate lifters which do not have any sharp edges. The particular lifters shown in the Goetz patent have "squared off" front and rear ends. It has been observed that wire, particularly small diameter wire, tends to bunch up at the squared ends of the lifters, resulting in tangling of the wire.
Therefore, the prior art wire coil blast cleaners having hard metal lifters, as taught by the Goetz patent, have serious disadvantages, some of which are discussed above. These disadvantages prevent the Goetz blast cleaning apparatus from achieving maximum efficiency in cleaning coiled wire.